A decrease in commercial fishing in George's Bank and an increase in the number of gray seals found off the New England coast seem to be factors in the recovery of the great white shark populations in the Gulf of Maine.

But there has been an apparent increase in their numbers since the 1990s.

A National Oceanic and Atmospheric Administration study released in 2014 and published in the journal PLOS One indicates that great white shark numbers are on the increase off the East Coast, although they still enjoy international protected status.

In the past, it has been hard to study these animals because they were so elusive. But because they are now targeting gray seals, researchers are able to tag and track them.

More than 30 of these fish are tagged and a ping locating them in the world appears every time they come near the water's surface.

A website follows them (see link below) and that is giving scientists and the public a lot more knowledge about where they go and what they do.

In these cold waters off New England, at the edge of their range, their prey of choice is gray seals.

Gray seals were hunted and used for fur until they became protected by the Marine Mammal Act of 1972. Since then, their numbers have been on the increase.

Allan Waterfield, vice chairman of the Seacoast Science Center in Rye, made a recent presentation on great white sharks, or white sharks. He said he feels there is an increase in their numbers in these waters because of the increase in the number of seals.

But he also noted that the reduction in commercial fishing due to stock depletion and the elimination of long-line fishing, where young sharks were a by-catch (or incidentally killed) may also be at play.

He noted there were once about 20 gill net boats out of Rye Harbor 20 years ago, but now there are only about four or five boats.

And during tournaments, sharks are now catch-and-release only. He noted the U.S. has also outlawed the practice of "shark finning," where the fins were taken off the sharks and sold for soup in the Orient.

Renee Zobel, a New Hampshire Fish and Game biologist, said the agency does not have a lot of interaction with sharks in general, although there are at least eight kinds of sharks known to swim in the Gulf of Maine.

It seems for great white sharks, the cold water line is at the end of Cape Cod. The cape appears at the northernmost edge of their summer range, but tracking shows the sharks move from Halifax, Nova Scotia, to Florida.

The Massachusetts Division of Marine Fisheries has much more action with these sharks than New Hampshire's biologists.

A report by the department on the great white shark resource indicated that 40 years of protection of the gray seal has set the table for sharks in these waters.

As "the gray seal population has rebounded, there is strong evidence that white sharks are expanding their foraging strategies to include active predation on these animals. For the first time, we have predictable access to white sharks," it read.

At the Seacoast Science Center, Waterfield noted that they have a very popular display of chain cat sharks, which are small by shark standards.

There are more than 360 types of sharks identified worldwide and they range from 8 inches to 60 feet long.

Chain cat sharks are about a foot long and they are bottom-dwellers in water 1,300 feet deep.

You can visit the Seacoast Science Center to see these sharks and also spend the day at Odiorne Point State Park, enjoying the tidal pools in the rocks.

The center, at 570 Ocean Blvd. in Rye, is open daily in summer from 10 a.m. to 5 p.m. with adult admission $10 and children 3-12 $5. There is a parking fee for Odiorne State Park and it is $4 per adult and $2 for children.

An interesting website that tracks tagged sharks is available. Each shark tagged has been given a name and you can track it, like Mary Lee, who was tagged off Cape Cod in 2012.